Method of corrugating or folding tubes.



L. H. BRINKMAN.

METHOD 0F CORRUGATING 0R FOLDING TUBES APPLCATION FILED JAN 11.1913.

Patented Dec 8. 1914.

2 SHELTS SHLITI m' l' 1m' a' JR.

in 4TH? NHS WITNESSES L. H. BRINKMAN.

METHOD 0F CURRUGATING 0R FOLDING TUBES.

APPLICATION FXLED JAN. 11,1913.

Patented Dec. 8, 1914.

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INVENTOR,

UNITED sTATEs PATENT oEEicE.v

LOUIS H. BRINKMAN, 0F GLEN RIDGE, NEW JERSEY, ASSIGNOB TO BALTIMORE TUBECOMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

METHOD OF COBBUGATING OR FOLDING TUBES.

Bpeclloation of Letters Patent.

Patented Dec. 8, 1914.

Application nled January 11, 1913. Serial No. 741,387.

To all whom it may concern.'

Be it known that I, Louis H. BRINKMAN, a citizen of the United States,and a resident of Glen Ridge, county of Essex, State of New Jersey, haveinvented certain new and useful Im rovementsl in Methods of Corrugatingor olding Tubes, of which the following is a specification.

My invention relates tolcorrugating tubes helically, and the inventionconsists in the method of corrugating or folding tubes helically, ashereinafter explained and more particularly pointed out in the appendedclaims.

Various methods and apparatus have been proposed for corrugating tubeshelically, in an attempt to form helically corrugated tubes with deepfolds to provide the flexibility or relatively great radiating surfacenecessary to the adaptation of such tubes to extensive fields of usesuch, for example, as for flexible connections, couplings, radiators,etc., but the methods and apparatus proposed for making such tubingeither stretch or crush and stretch the metal into folds withouttwisting the metal, and this twisting I have found to be essential indeeply corrugating tubing. The methods and apparatus which have beenproposed are such that the deeply corrugated tubes desired can not becommercially manufactured, and so far as I am aware, heretofore it hasbeen impossible to commercially manufacture corrugated tubes with foldsor corrugations of such depth as to render the tubes really iexible, andprovide a relatively great radiating surface.

By the use of my invention helically corrugated tubes of considerablelength may be readily made, the length of the corrugated tube beinglimited only by the length of the tube to be'corrugated, and thecorrugations or folds may be of extreme depth so as to provide a tube ofgreat flexibility and relatively large radiating surface.

ln carrying out my invention, the metal of the tube is folded in such amanner that it is not wrinkled or materially thickened or spun outduring the folding process, and in practicing the preferred form of theinvention, the wall thickness of the tube remains substantiallyunchanged during the folding process.

These results are made possible by twisting the metal of the tube, andwhile twisting it pressing upon it alon a helical line along which themetal will fo d, the pressure being exerted upon the wall of the tube ata progressively shifting short portion thereof and the actual twistingofthe metal being localized to substantially the short portion of the tubebein pressed upon or the short portion being olded, so that the portionof the tube which has been folded to the d esired final form isprotected from distortion by the twisting force. The twisting of itselftends to fold the tube by distorting 1t helically and contracting itlongitudinally, and thus greatly reduces the pressure re guired on themetal to deepen the folds, and if continued after the folds are thusformed, 1t reduces the pitch of the folds and increases their depth bycontinuously forcing the folds around helically analogous to the mannerin which a helical spring of a certain pitch and diameter may be reducedin diameter and pitch by slipping it over a rod to prevent buckling, andholding one end down on the rod While twistin the rod and holding the oposite end o the spring from rotation, whi e permitting it to move alongthe rod.

In `deeply corrugating tubing, I have found that it is of greatimportance, if not essential, to apply the pressure along the helicalline inwardly against the wall of the tube. When the pressure is exertedlfrom the outside inwardly on the tube to form the folds by displacingthe nietal inwardly, the diameter of the pressed-in metal is less thanthat of the original tube; hence there is more than sufficient metal forthe circumferential measurement of the folds and the metal does not haveto be stretched or spun out in forming the folds as would be the case ifthepressure was exerted from the inside outwardly. The metal is crowdedin as it is pressed inwardly, producing what without the twisting of themetal would be an excess of metal along the helical line of pressure,such as takes place when it is attempted to force the metal of a hollowcylinder or tube inwardly at any point along its length to reduce thediameter at that point; in which event, by being crowded in along theline of reduced diameter, the metal is caused to wrinkle or pucker. Thiscrowding of the metal would soon limit the depth of the folds if it werenot for the twisting force above mentioned; but by producing a twistingforce in the tube to actually twist the metal, und-while the tube isunder such force, pressing inwardly on it along a helical line, theexcess metal is displaced helically as it is being forced inwardly so asto keep the wall substantially uniform in thickness during the foldingprocess, permitting the formation of folds of great depth.

The resistance of the metal of a tube to inward pressure is so greatthat suicient friction between the corrugating tool and the metal isproduced to twist the tube, and because of this resistance the metal canbe gripped and drawn together along the length of the tube to form theaxial sectional configuration of the folds and otherwise formed into thedesired shape without appreciable stretching or spinning of the metal.

In corrugating tubes according to the more preferred form of myinvention, I initiate a helical groove in the tube of such pitch as tomark out along the tube suiicient metal to form an ultimate fold of thedesired depth and pitch without substantial change in wall thickness,and progressively increase the depth of the groove and decrease itspitch by simultaneously pressing inwardly on the metal along the groove,drawing together its convolutions and twisting. By marking out along thetube substantially enough metal to form the ultimate fold of the desireddepth and pitch sufficient metal is provided to form th fold withouthaving to spin or stretch from a less amount of metal a sufficientlength to form the axial sectional configuration of the fold. Thisfeature and the twisting, permit the tube to be folded or corrugatedwithout substantially changing its wall thickness. By pressing on thefolds while they are bein formed, they may be made to assume di erentdesired cross-sectional configurations, depending upon the an le atwhich the pressure is exerted upon t em.

In corrugating tubes according to the preferred manner of practicing myinvention, I rotate the forward end of the tube at a certain speed androtate the rear end of the tube at a less speed, and groove it at aspeed having a definite relation thereto, the ratio between the speedsbeing constant so as to produce a positive and constant twisting forcein the tube to reduce uniform corrugations or folds in t e finishedtube; and when desired, I bend the folds longitudinally toward one-endof the tube while they are being formed. In order to limit the itch ofthe ultimate folds and their dept and to hold the tube from bucklingduring the folding or corrugating process, or, in other words, tolocalize the twisting of the metal substantially to the progressivelyshifting short length of the tube being pressed upon or to the proressively shifting short length being fo de I provide an inner supportupon which the tube 1s folded. With this inner support the inwardpressure may be progressively applied by the tool until the depth of thegroove in the tube is ositively limited by coming in contact wit thesupport, whereupon, if there should be any irregularities or unevennessin the metal of the groove, the tool will act to smooth or iron out anyunevenness in the metal.

rI he actual twisting of the metal is not limited strictly to thatportion of the tube being pressed u on by the tool or Within the tool,for the too in most cases will not bring the metal down upon the innersupport with sufficient friction to prevent the metal of the folds asthey leave the tool from being twisted until they are brought down onthe support. In some cases the folds as they leave the tool may not eventouch the mandrel, and therefore the last few folds adjacent the mandrelwill also be twisted to bring them firmly down upon the mandrel or innersupport. When, therefore, I refer to the actual twisting being localizedto the portion of the tube being pressed upon or gripped, I wish to beunderstood as meaning not only the portion of the metal immediatelywithin the tool, but also the few folds adjacent the tool which have notyet been brought down with suliicient friction upon the inner support toprevent further twisting.

In order to prevent distortion or mutilation of the forward end of thetube in starting the corrugations under the powerful twisting forcenecessary, I first draw down the end of the tube to form a taperingportion the small end being of such diameter as to fit upon the innersupport. In pressing upon the tube I commence at the point where thetube diverges from the inner support, so that the tube is from the startorced into firm engagement with the inner su port to prevent itsdistortion.

y invention will be more readily understood and further objects of theinvention will more fully appear from the following description taken inconnection with the accompanying drawings showing the preferred form ofapparatus for carrying out the process, in which- Figure 1 is a frontelevation of the machine, showing a tube in process of corrugation; Fig.2 1s an enlarged view of a part of the mechanism showing the corrugatingtool or die partly in section and in position to commence corrugatingthe tube; Fig. 3 is a view showing the die and a part of the mamas?corrugated tube in section; Fig. 4 is a crosssectional view of the dieshown in Fig. 2, taken on line A--A and looking in the direction of thearrows B; Fig. 5 1s a fragmentary sectional view showing a modified formof corrugating die in process of operation; Figs. 6, 7, 8and 9 showdifferent forms of tube corrugated by said machine; Fig. 10 illustratesthe manner in which the metal of the tube is twisted or carried aroundhelically as it is bein compressed; and Fi 11 is a diagrammaticillustration.

ferring to the drawings, Fig. 1 is a front elevation of a suitablemachine frame 1 having a head stock 2 and a tail stock 3. 4

is a shaft journaled in the head stock 2 and block 5 and driven throughcounter pi low pulley 6. The

any suitable means such as inner end of the shaft is rovided with achuck 7 Fig. 2) to whic is secured the tube 8 to be corrugated orfolded, and also an inner support or mandrel 9 which extends through thetube, the tube and mandrel being secured to the chuck by any suitablemeans such as set bolts 10, 10', so that they will revolve together withthe chuck. A carriage 11 of suitable construction is slidingly mountedon the frame 1 and is moved longitudinally alon the same by means of ascrew spindle 12 ournaled in the head and tail stocks and driven fromshaft 4 through suitable gearing 13, the gearing being arranged like theusual lathe gearing so that the s eed of the screw spindle 12 may bevarie depending upon the work to be performed. On the carriage 11 ismounted a suitable chuck 14 of the usual construction, but in which forthe usual radiall adjustable gripping jaws, are substitute radiallyadjustable die sections 15, 16, 17, 18. These sections are movedradially by adjusting pins 19 each carrying at its inner end the usualbevel gear meshing with the gear teeth 20 cut on one side of ring 21 onthe other side of which are formed the spiral threads 22 which mesh withthreads 23 for the purpose of moving the die sections in and outradially to adjust the diameter of the die. The inner ends of these diesections are tapered as shown at 24 in Fig. 4, to permit the desiredradial adjustment, and the inner ends of the sections are provided withprojections 26, 27, 28, 29 which, when the die sections are assembled,form a thread or helical projection increasing in hei ht and decreasingin pitch toward the nishing end of the die. In the referred form of theinvention as shown erein, the projections of each section of the dieconstitute longitudinal sections of a continuous thread or helicalprojection progressively increasin in height and decreasing in pitch, sothat W en the die is assembled, the projections of the different diesections form such a helical projection.

In the form of apparatus herein shown, a hollow tail shaft 30 isprovided extending throu h a sleeve 3l journaled in tail stock 3, thetall shaft being secured at its inner end by a suitable chuck 32 to therear end of the 70 tube B. The purpose of this tail shaft is to producea positive predetermined twist in the tube being corrugated, and forthis purpose the tail shaft is rotated at a speed less than the speed ofshaft 4, the difference in? speeds being such as to produce the desiredtwist in the tube while it is being folded. This tail shaft may berotated by any suitable means to produce this result, and in the presentform of apparatus the shaft is proio vided with a groove 33 in whichfits a suitable feather (not shown) projecting inwardly from the sleeve31 to cause the shaft to rotate with the sleeve and permitting it tomove longitudinally through the sleeve.

tardin force which is produced by the rota-'f tion o the tail shaft atless speed than the rotation of the finishing end of the tube, may beobtained by gripping the rear end of the tube 8 in any suitable mannerto retard its rotation, such, for instance, as by ai friction grip whichwill permit it to be rotated but at less speed than it would be rotatedif it were held back simply by the friction of the die.

Referring to Figs. 2 and 3, it will be observed that the helical dieteeth or projections are so constructed that the advance projectionsimply initiates in the tube a helical mark or groove along which thetube is to be folded, and by thus start-ing a. groove in the tube itgives it a. line of least resistance along which to fold under thetwisting force. It will also be noted that the advance convolution ofthe helical projection marks out along the length of the tube sufficientmetal to form the axial sectional configuration of the desired fold inthe ultimate product; that is, the distance between points 36 and 37 isequal to the length of the curved out line between points 38 and 39.

By marking out along the tube suflicient metal to form the sectionaloutline of a fold of the desired depth and pitch, it is ossible to formthe desired folds accordlng t my invention without appreciablylstretching or spinning out the metal, as hereinbefore explained. It willbe further observed from inspection of these drawings, that the greatestdiameter of the helical groove of the die is the same throughout the lenof the oove andis equal the diemetegrtllif the tugera to be corrugated.his insures the diameter of the corrugated tube being the same as theoriginal, diameter of the tube, since it positivel prevents any outwardexpansion of the tu e durin the folding process, and the outer surfae othe folds may be made to assume an outline depending upon the outline ofthe rooves between the projections of the die. hen a die of thischaracter is used and relative rotation 1s produced between the tube andthe die while the tube is gripped by the die, the friction produced isso great that the tube 1s twisted, and as the metal of the tube underthis twisting force and the relative longitudinal movement between thedie and the tube, is drawn through the helical path or grooves in thedie, the helical line along which the tube is gripped by the advanceconvolutions of the die is gathered or drawn together in forming thefolds. Thelfrictlon produced by a corrugating tool or die of thischaracter is so great that sutlicient friction is obtained forcorrugating tubes of certain sizes without the use of any means forretarding the rear end of the tube or for positively driving it at lessspeed than the front end to produce a positive twisting force. Tubes aslarge as 3 inches in diameter and with walls a thirty-second of an inchthick, have been successfully corrugated by such dies without anyadditional retarding force applied at the rear of the tube, but theapplr cation of a retarding force at the rear end of the tube makes itpossible to utilize a tool having less friction, and whether or not thisbe taken advantage of, it produces corrugations of greater uniformityand enables tubes of greater wall thickness to be more readilycorrugated.

When it is desired to form tubes of a given size but with greaterflexibility and larger radiating surface than is possible with the dieshown in Figs. i2 and 3, means may be provided for pressinglongitudinally on the folds while they are being formed so as to bendthem toward one end of the tube as shown in Figs. 5, 8 and 9. This isdone in the form of apparatus herein shown (Fig. 5) by gradually turningthe edges of the helical projections longitudinally at the finishing endof the die so as to progressively bend the folds longitudinally as theyare being deepened. I have found it preferable to commence thislongitudinal turning over or bending of the helical projections at aboutone and a half convolutions from the finishing end of the die and`radually increasing the longitudinal projection until it is of suchdepth as to ive the desired shape to the ultimate old. While I haveshown these projections with longitudinally bent edges as an integralpart of the die sections, obviously they need not be :made integralwithl theremaxning' partof the sections. Besides obtaining rugated tubesof greater flexibilt diatin surface by bending the 0 dS. 10 I tudina lyas shown in Figs. 5, 8v and 9,1151; bending of the folds in this mannerenables the corrugated tube to be ,more/2 readily drawn .from themandrel, since the. folds, instead of bearing down pe ndicularly uponthe mandrel, are inclinexdmor so constructed that the will more readilyyield when the mandre Ais drawn out. Y

In the drawings herein shown, the mandrel is of suchldiameter withrespect to the setting of the die, that 'the last tooth of the die foldsthe tube down upon the mandrel; but if desired, the finishing tooth orconvolution need not come down so close to the mandrel, and the twistinof the tube after it leaves the finishing en of the die may be reliedupon to finish the folding of the tube down upon the mandrel.

The corrugating or folding of tubes according to my invention by the useof the form of apparatus herein shown for carrying ont the invention, isas follows: The tube 8 to be folded is preferably, though notnecessarily, drawn down to a taper near its forward end so as to fit theta er of the die, and the tube is then slippe over the mandrel and themandrel and tube are secured in the chuck 7 in any suitablemanner so asto rotate together with the chuck. The hollow tail shaft 30 (when one isused) is then pulled forward through the sleeve 3l and after the rearend of the mandrel has been slipped into it, the rear end of the tube 8is secured in the chuck 32, and the carriage 1l being up at the head ofthe frame to bring the die in the position shown in Fig. 2, the sectionsof the die are radually moved inwardly by turning one og the pins 19until the helical projection formed by the different projections on thedie sections, grips the tube along the tapered portion. If power is nowthrown on to rotate shaft l, the mandrel and front end of the tube Willbe rotated, and simultaneously therewith the threaded spindle 12 will berotated to move the carriage along the tube and to rotate the tail shaftand rear end of the tube at a definite predetermined speed less thanthat at which the forward end of the tube is being rotated so as topositively twist the tube a predetermined definite amount, dependingupon the relative rotation between the forward and rear end of the tube.As the die is moved along the tube, the advance point 36 of the helicalprojection progressively marks or initiates a helical groove in thetube, and the metal marked out by the first convolution of the helicalprojection, as, for example, the metal between points 36 and 37, isgradually drawn together as the pitch of the helical projectiondecreases, and

cdrand ralines along whic i in dotted lines; but by anche? since theheight of the projection progressively increases as the itch decreases,the metal along the helca line is gradually and progressivel pressedinward y as the the tube is gripped are drawn together; and as the metalis being gradually forced in by the helical projection, the excessmetal, due to the reduction in the diameter along this line, isgradually displaced by the twisting force exerted on the tube, asindicated, by way of illustration, by the direction of the arrows inFig. 10. This twisting force, as previously stated, not only displacesthis metal under the inward ressure so as to permit the deepening o thegrooves to the desired extent without wrinling or rupturing the metal,but the twisting in itself tends to fold the tube helically along theline of least resistance produced by the helical groove initiated in thetube. As the die carriage is moved along the tube, the die progressivelymarks the tube in this manner and the twistin force is continuouslyapplied as describe The ellect of the twisting force in the gradualdrawing toether of the metal of the tube into helical olds may beillustrated, in a way, by reference to Fig, 11, in which 45 is a rod ormandrel to the end 46 of which is secured a helical spring or piece ofspring wire which is wound around the rod with a progressivelyincreasing pitch from the end 46. If it is attempted to draw theconvolutions of the spring toward end 46 so as to decrease the pitch ofthe longer convolutions as shown at the end 46 of the mandrel withoutrotating the mandrel or the free end of the spring, as the convolutionssay at points 47 and 48, are gripped and drawn together, theconvolutions of the spring between these points will rise from themandrel as shown gripping the convolutions at the free end o the springso as to hold them from rotation, then rotating the rod in the directionshown by the arrow 49 and gradually drawing the convolutions togethertoward end 46, the spring will be folded down firmly upon the rod in thedesired decreased pitch without increasing its diameter and without anytendency to buckle out of the desired form of the spring. During thisrotation of the rod the spring will actually slide along and move aroundthe mandrel in a helical line as indicated by the arrows 50. In asomewhat similar manner, when a tube is being folded according to mymethod of folding tubes, the twisting force applied actually displacesor carries the metal around helically so that the resulting corrugatedtube formed under the twisting force is actually slightly longer thanthe tube would have been if it could have had similar corrugationsformed in it without the twisting force.

The amount that the tube may be twisted in forming the folds may bevaried in several ways such as by varying the relative rate of rotationof the advance and rear ends of the tube, or by varying the pitch of thedie relative to that of screw shaft 12, or the speeds of the shafts 4and 12. v

In practice I have found that it is very important to provide a supportfor the tube being corrugated, such, for example, as the mandrel. Such asupport is an important feature in regulatin the action of the twistingforce on the fol s, and by the regulation of this force, folds of thedesired configuration and size may be formed. For example, when thefinished folds are brought down firmly upon the support and onlysuiiicient relative rotation between the shafts 4 and 30 is produced todisplace the metal as it is being pressed upon by the die, or to bringthe folds down upon the support after they leave the die, where thesupport is of less diameter than the die, the friction between the foldsand the support is sufficient to prevent relative rotation between thesupport and the folds which have been forced firmly into engagementtherewith, so that the support will serve to localize the twisting forcein the tube by transmitting the force from the chuck to the portion ofthe tube being folded down upon the support. By reason of this the foldsthat have been brought firmly into engagement with the support areprotected from further effects of the twisting force, so that the tubemay be deeply corrugated under the twisting force and the pressure ofthe die, without crowding together the folds after they have been forceddown firmly into engagement with the su port. If, however, it is desiredto force t e folds more or less together to change the sectionalconfiguration of the same, and to decrease their pitch after they havebeen forced 'firmly into engagement with the support, this may be doneby decreasing the longitudinal travel of the die with relation to thepitch of its helix. I have found that without a suitable support, thetube under the twisting force necessary to deeply corrugate it, willtwist up and buckle, since only a very short length of tube can transmitthe twisting force necessary to overcome the friction of the die withoutbeing distorted; and again the corrugations formed would, under suchforce, likewise be twisted and distorted out of the desired shape andsize.

In Fig. 6 the dotted helical line 52 represents the seam of the originaltube which was corrugated, and illustrates the relative amount of twistin the corrugated tube for a given length. If, in corrugating tubing inthe shape shown in Fi 6, the shaft should be driven at 38 revo utionsand the tail shaft 30 at 32 revolutions, there would be a difference of6 revolutions representing 6 complete twists in the tube, and if thepitch of the screw shaft 12 and the corrugated pipe 8 is inch, and thescrew shaft is driven at 38 revolutions a minute, the corrugated tubewill have been completely twisted 6 times for every 9% inches.

Fig. 7 shows the manner in which the folds or corrugations are forcedtogether when the relative diameters of the die and the mandrel are suchthat there is a clearance between the folds of the tube and the mandrelas the folds leave the die, in which case the twisting force due to therelative rotation of the mandrel with respect to the die, will furthertwist the corrugated tube until the folds are drawn by the twistingforce firmly together, as shown in Fig. 7 or the crowding of the foldsalong the mandrel may be accomplished in another manner by decreasingthe speed of the shaft 12, as previously pointed out.

Fig. 8 shows one form in which tubes may be corrugated with a die havinga portion of its projection near the finishing end bent longitudinallysomewhat in the manner shown in Fig. 5, but the teeth or projections ofthe die being so formed that one wall of each fold remains upright Whilethe other wall of the fold is bent in such a manner that each foldoverhangs on one side the adjacent groove; whereas, in Fig. 9 the entirefold droops over to one side.

In referring to the helical contour or thread of the tool or die, I haveused the terms helix, helical projection and helical projectionssomewhat synonymously and interchangeably, because the projections ofthe tool or die sections, when assembled, form a continuous helicalprojection; and in so far as the principle of my invention is concerned,it may be regarded as a unitary solid helical projection, or as composedof a greater or less number of projections than those herein shown. Forconvenience of description, I have also used the terms folds7 and eachfold in referring to the corrugated or folded tube, since eachconvolution of the helically folded tube may be considered as a. fold.

While I have shown and described the preferred form of apparatus forcarrying out my process, and have described the process in detail inconnection with the form of apparatus shown, so as to enable thoseskilled in the art to more readily understand the invention and practiseit with such apparatus, it will he understood that the invention can becarried out by different forms of apparatus from that herein shown anddescribed, and that, in the light of my invention, those skilled in theart may be able to modify or change prior apparatus and the proposedoperation of the same so as to enable them to be used for corrugatingtubing according to my invention, and I do not Wish to be understood aslimiting myself other than as indicated in the appended claims.

I make no claim herein to the ap aratus for corrugating tubes, or thepro uct in corrugated tubes, since the apparatus and product form,respectively, the subject-matter of my coending applications Serial No.741,390 and Serial No. 741,388 each filed on even date herewith. V

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. The method of forming flexible corrugated tubes, which consists inpressing upon a tube along a helical line of decreasing pitch andsimultaneously twisting the portion of the tube bein pressed upon todisplace the excess meta along said line as it is being compressed.

2. The method of forming flexible corrugated tubes, whch consists ininitiating in a tube a helical groove of less depth and of greater pitchthan desired in the ultimate' product and deepening the groove anddecreasing the pitch by twisting the grooved metal and simultaneouslyand progressively pressing inwardly on the tube along the helical groovewhile twisting it so as to displace the excess metal being compressedalong the groove infdeepening the groove and decreasing its pitch.

3. The method of forming flexible corrugated tubes, which consists 1nprogressively initiating a helical groove in the metal of such pitch asto mark out along a tube suiicient metal to form a fold of the desireddepth and pitch in the ultimate product without substantial change inwall thickness and simultaneously deepening the groove and decreasingits pitch by continuously twisting the grooved metal and graduallypressing it inwardly while twistin it.

4. The method of forming flexi le corrugated tubes, which consists 1nprogressively gripping a tube along a helical line of decreasing pitch,the pitch of the advance convolution being such as to mark out along thetube a suflicient length of metal to form an ultimate fold of thedesired depth and pitch without substantial change in wall thickness,and twisting the tube and by the aid of such twisting drawing togetherthe gripped metal into helical folds.

5. The method of forming flexible corrugated tubes, which consists inprogressively forming in a tube a helical groove of less depth and ofgreater pitch than desired 1n the ultimate product and progressivelyincreasing the depth of the groove and decreasing its pitch bvsimultaneously pressing inwardly on the metal alon the groove, drawingtogether its convo utions and twisting it.

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6. The method of forming exible corrugated tubes, which consists inprogressively initiating in a tube a helical groove of such pitch as tomark out sufficient metal along the tube to form an ultimate fold of thedesired depth and itch without substantial change in wall thickness, andprogressively increasing the depth of the groove and decreasing itspitch by simultaneously pressing inwardly on the metal along the roove,drawing together its convolutions an twistin it.

The method of forming fiexible corrugated tubes, which consists in griping a tube along a helical line and pr ucing a continuous twistingforce therein, and while producing such twisting force progressively andsimultaneously drawing together the convolutions of the helical linealon which the tube is thus gripped and positive y forcing the metalinwardly along said line.

8. The method of forming flexible corrugated tubes, which consists ingripping a tube along a helical line of greater pitch than desired inthe ultimate product, and progressively drawing together theconvolutions of the helical line along which the tube is gripped andsimultaneously therewith progressively forcing the metal along said lineinwardly and twisting it to assist in gathering together the helicalfolds and to move the excess compressed metal along a helical path.

9. The method of forming flexible corrugated tubes, which consists ingripping a tube along a helical line and producing a continuous twistinforce therein, and while producing such twisting force progressively andsimultaneously drawing together the convolutions of the helical linealong which the tube is thus gripped and positively forcing the metalinwardly along said line, and decreasing the pitch of the folds bytwisting the metal thus folded.

10. The method of forming flexible corrugated tubes, which consists ingripping a tube along a helical line and producing a continuous twistingforce therein serving to actually twist the metal of the tube, and whileproducing such twisting force progressively and simultaneously drawingtogether the convolutions of the helical line along which the tube isthus gripped and positively forcing the metal inwardly along said line,while confining the shell of the tube from outward expansion.

11. The method of forming flexible corrugated tubes, which consists inprogressively gripping a tube along a converging helical line ofdecreasing pitch and simultaneously and continuously twisting the tubeto cause the gripped metal to be gradually drawn together longitudinallyof the tube into helical folds.

12. The method of forming flexible co1'- rugated tubes, which consistsin producing a twistin force in a tube to twist it helically an contractit. longitudinally and simultaneously and progressively initiating ahelical groove in the tube to rovide a. line along which the tube may efolded under the twisting force, and gradually and simultaneouslygathering the grooved metal into helical folds.

13. The method of forming flexible corrugated tubes, which consists inproducing a twistin force in a tube to twist it helically an contract itlongitudinally and simultaneously and progressively initiating a helicalgroove in the tube, to provide a line along which the tube may be foldedunder the twisting force, and gradually pressing inwardly on the tubealong said groove and simultaneously gathering the grooved metal intohelical folds.

14. The method of forming flexible corrugated tubes, which consists ingripping the metal along a helical line of decreasing pitch, andcontinuously twisting the finishing end of the tube while retarding therear end so as to cause the gripping metal to be drawn under thetwisting force into helical folds of the desired depth and pitch.

15. The method of forming flexible corrugated tubes, which consists inrotating the ends of a tube in the same direction at different rateshaving a constant relation to twist the tube, and while thus twistingthe tube, gripping it along a helical line of decreasing pitch to causethe gripped metal tobe drawn together under the twisting force intohelical folds of the desired depth and pitch.

16. The method of forming flexible helically corrugated tubes` whichconsists in pressing upon the wall of a tube along a helical line andsimultaneously rotating the ends of the tube in the same direction atdifferent speeds having a constant relation to twist the tube and causethe metal being pressed upon to be folded into folds having acontinuously uniform amount of twist, and protecting the finished foldsfrom distortion by the twisting force.

17. 'I he method of forming fiexible helically corrugated tubes. whichconsists in pressing upon the wall of a tube along a helical line andsimultaneously rotating the ends of the tube in the same direction atdifferent speeds having a constant relation to each other and to therate at which the folds are being formed to twist the tube and cause themetal to be folded into helical folds having a uniform pitch and amountof twist.

18. The method of forming fiexible helically corrugated tubes` whichconsists in continuously twisting the tube and gripping the twistingportion of the tube along a helical line of decreasing pitch at aprogressively shifting short length of the tube in the carrying out ofwhich the gripping means is positively moved continuously along the tubeat a uniform rate with respect to the amount of twist being produced inthe tube to produce symmetrical folds.

19. The method of forming flexible hel-ically corrugated tubes, whichconsists in gripping the tube along a helical line of decreasing pitchat a pro ressively shifting short length thereof an simultaneouslyproducing a twisting force i'n the tube and localizing the twistingforce to the length of tube being folded, in the carrying out of whichthe gripping means is continuously moved along the tube at a uniformrate with respect to the amount of twist being' produced in the tube soas to produce symmetrical folds.

20. The method of form-ing helically corrugated tubes which consists inprogressively gripping the outer surface of a tube along a helical lineof decreasing pitch` and producing a twisting force therein sufficientto actually twist the metal of the tube and b v the aid of such twistingdrawing together the grippedmetal into helical folds, and simultaneouslywith such operation protecting from further twisting the folds whichhave been formed of the desired pitch.

21.The method of forming flexible corrugated tubes, which consists inprogressively gripping the outer surface of a tube along a converginghelical line of decreasing pitch and simultaneously and continuouslytwisting the tube and by the aid of such twistin gradually drawingtogether the grippe metal and folding it down upon an inner support intohelical folds of the desired depth and pitch.

22. The method of forming flexible helically corrugated tubes, whichconsists in twisting a tube and while twisting it pressing upon it alonga helical line to fold the metal helically and draw the folds down uponan inner support serving to prevent the finished folds from beingtwisted out of their desired shape and to localize the twisting of themetal to the portion of the tube being folded.

23. The method of forming flexible helically corrugated tubes, whichconsists in twisting a tube and while twisting it pressing upon -italong a helical line to fold the metal helically and while thus twistingand pressing upon the metal positively limiting the depth of the foldsbeing formed and protecting the folds thus formed from further effectsof the twisting force.

24. The method of forming flexible helically corrugated tubes, whichconsists in gripping a tube along a helical line at a progressivelyshifting short length of the tube and producing a twisting force in thetube to fold the metal helically While localizing the twisting to theportion ofthe tube being folded, an simultaneously, by means of Vthegripping means, positively confini'ng and guiding the folds under thegripping pressure and the twisting force, into a predetermined shape.

25. The method of forming helically corrugated tubes, which consists informin helical folds in a tube and bending sai folds over longitudinallyto one side of the helical axis.

26. The method of forming helically corrugated tubes, which consists ingradually and simultaneously gathering the metal alon the length of thetube into helical folds an bending over a wall of each fold as the foldis being formed.

Q7. The method of forming helicall corrugated tubes, which consists ingra ually folding the metal of a tube into helical folds, and bendingeach fold longitudinally while forming it.

28. The method of forming helically corrugated tubes, which consists inproducing an actual twisting of the metal at a pro` gressively shiftingshort length of the tube and positively guiding the metal bein twistedinto helical folds and bending eac fold longitudinally while forming it.

29. The method of forming flexible corrugated tubes, which consists inprogressively gripping a tube along a helical line of decreasing pitch,the pitch of the advance convolution being such as to mark out along thetube a suflicient length of metal to form an ultimate fold of thedesired depth and pitch without substantial change in wall thickness,and twisting the tube and by the aid of such twisting drawing togetherthe gripped metal into helical folds, and pressing a wall of each foldover longitudinally while forming the fold.

30. The method of forming flexible corrugated tubes, which consists inpressin upon the metal of a tube along a helica line of decreasingpitch, and twisting and drawing together the metal while pressing uponit.

31. The method of forming flexible helically corrugated tubes, whichconsists in gripping the metal along a helical line at a progressivelyshifting short length of the tube and while pressing upon it along saidline actually twisting it at said progressively shifting short length.

The method of forming flexible helically corrugated tubes, whichconsists in producing an actual twisting of the metal at a progressivelyshifting short length of the tube and positively guiding into helicalfolds the metal being twisted.

33. The method of forming exible helically corrugated tubes, whichconsists in In testimony wbereof, bave signed my grossing upon the wallof the tube along a name to this speication, in the presence of 10elical line and simultaneously g'oduclng two subscribing Witnesses.

a. twisting force in the tube su cient to actually twist the metal andlocalizing the actual twisting of the fnetal by said force tosubstantial y the length of the tube pressed upon.

LOUIS H. BRINKMAN.

Witnesses:

EDWIN Snom, SAMUEL M. WARD, Jr.

u I which consists in In .testimony whereof,"I `have signed mycarlelgsincgriilpitlie twg-lla of the tube along a name to thisspelicatlom 1n the prence of 10 helical line and simultaneously roduelngtwo subscribing witnesses. j

a twisting force in the tube su c ient to LOUIS H BRINKMALL 5 actuallytwist the metal and locallnlng the actual twi'stin of themetal by saldforce Witnesses.

h f th tube EDWIN Smm, essslldstiipldil y the lengt o e SAMUEL M. WARD,Jr.

It is hereby certified that in Letters Patent No. 1,120,267, grantedDecember 8,- 1914, upon*` -the application of Louis H. Brinkman, of GlenRidge, New Jersey, for

an improvement in Methods of Uorrlugating or Folding Tubes, an errorappears.

in the printed specification requiring correction as follows: Page 7,line 91, for the word gripping read gripped; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the case in the Patent Oice.

' signed and sealed this 25th day of May, A. D., 1915.

[SEAL] R.l WHITEHEAD,

I Actng ommz'uoner of Patenti?.

It is hereby certified that in Letters Patent No. 1,120,267, grantedDecember 8, 1914, upon the application of Louis H. Brinkman, of GlenRidge, New Jersey, for

an improvement in Methods of Corrugating or Folding Tubes, an errorappears in the printed specification requiring correction ne follows:Page 7, line 91, for the word gripping read gripped; and that the saidLetters Patent should berend with this correction therein thalt the samemay conform4 to the reeord of the esse in the Patent Oice.

' signed and sealed this 25th day of May, A. D., 1915.

R. WBITEHEAD,

Acting C'ommsoner of Patents.

